Be it known that I, CLARENCE R. KING, a citizen of the. United States of America residing at Worcester, in the county 0 Worcester and State of Massachusetts, have invented certain new and useful Improve-v ments in Polishing Wheels, of which the following is a full, clear, and exact s ecification.

My invention relates to the a rasive art and more particularly to abrasive wheels for The operation of olishing is that by which rough. surfaces le after forging, rolling, etc., or scratches and tool marks are removed and a smooth finish secured. The wheels ordinarily utilized for this operation are either wooden wheels covered with leather and turned to fit the piece to be polished or.

up a wheel being laborious, expensive an requiring the services of a skilled operator. When it is considered that set-up w eels of this type may be serviceable for polishing but a very few articles before the abrasive surface must be recoated, it will be seen that it is highly desirable to utilize a wheel which has abrasive throughout a considerable portion of its volume so that it may wear down to a smaller size and still retain its abrading characteristics. i

In polishin surfaces. of uneven contour, it is essential t at the polishing wheel have a slight degree of resiliency in its bod so that the outer abrading surface may f0 ow the shape of the article. Hence the ordinary grinding wheels made of a rasive grams a bonded with vitrified clays or similar hard substances are not well adapted for such polishin purposes. It 1s accordingly an object of m invention to overcome these difiiculties an to rovide an economical and serviceable polishing wheel which has a resilient body and is able to conform to a'contour and which, unlike the abrasive coated, set-up wheels, has abrading material throughout a considerable ramade in accordance with m dial depth and retains its abrading characteristlcs during repeated use.

With this and other objects in view as will be apparent in the 'following'disclosure, my invention resides in the construction of a polishin wheel as set forth in the specifica tion an covered by the claims appended hereto.

I have illustrated one embodiment of my invention by which:

Fi grin g wheel;

Fig. 2 is a detail in perspective" of the r silient body of the wheel shown in Fig. 1;'

Fig. 3 is a similar view of one of the abrasive strips; and

Fig. 4 is a perspective view, partly broken away, of a modified form of my invention.

I have discovered that the essential requirements are met by an abrasive article havin a resilient cushiomnfi' bod and space surface portions or teet of a rasive material united therewith, which is adapted forpolishing. The spaced abrading teeth, in addition to bein' resiliently supported, are separated by we of resilient material, to give the desired flexibility and permit the abrading .portions to be yieldinfly held against the surface being treate These teeth, which are preferably made of bonded abrasive grains, may be of regular geometrical patterns or irregularl shaped and spaced, the essential feature sin that they are so spaced and supported. as to e movable,

with the desired degree of freedom and 'yet have high po or grinding abihty. This may be vaecomp ished.by mounting or embedding=the abra resilient body made pre erably of rubber.

One type of a polishing wheel may be invention as shown in Figs-'1, 2 and 3. he center portion 10 of the wheel maybe made of a resilient material, such as rubber, having radial projections or webs 12 between which are inserted the spaced abrading teeth 14. These teeth may be in the form of parallel strips made from suitably bonded abrasive grains and formed into a unitary structure with the center portion by vulcamzation or other teeth in a central the accompanying drawings in re 1 is a perspective view of a resilient method. A central hole 16 is provided for the subsequent mounting of the wheel upon a spindle conforming .with the equipment with which it is to be used.

For certain purposes, it is preferable that the teeth be of irregular shapes interspersed throughout the resilient body. As shown in Fig. 4, such a wheel may be made of a rigid center 20'provided with a hole 21 and a dovetailed slot 22 in the periphery into which is fitted an abrasive ring 23. In this type of wheel, the resilient body 24:,which may be of desired radial thickness, carries the abrasive portions 25 in its outer annular zone or in certain instances distributed throughout its whole volume, as illustrated.

In one method of making a grinding or polishing wheel in accordance with my invention, a mixture is prepared of rubber, a vulcanizing agent such as sulphur and a suitable filler such as barytes or abrasive grains of suitable size, in which the ingredients are thoroughly distributed throughout the mass. A suitable composition which will give the desired degree of resiliency may contain the following materials in the proportions given:

h(A) 86.7% filler, 12.6% rubber, 0.7% sulp ur. v

This mixture is rolled out into sheets of convenient thickness and cut into the desired shape by means of dies, all of which is common practice in the art. For example, to make a wheel of the type shown in Fig. 1, which is a convenient shape for some purposes, disks 10 (Fig. 2) are formed with the radially projecting webs 12 and slots 18 and a hole 16 in the center for the bushing on which it is to be mounted when in use. In order to make a thick wheel, I employ two or more of the thin disks shown in Fig. 2, and place them face to face in the vulcanizing mold, so that they when vulcanized may form a solid body! of desired thickness as determined by the number of disks emplgyed 11 like manner, the hard abrasive strips or teeth 14 (Fig. 3) are moldjegdof such size andshape a -fit the slots at the cylinder which has be hus formed. The teeth are formed of abrasive grains bonded with any suitable bond employed in this art. A mixture adapted for this part of the wheel may be composed as follows:

(B) 86.7% abrasive grains, 8.9% rubber, 4.4% sulphur.

These strips are inserted into the slots of the body formed of the superimposed disks 10 and the complete .wheel'then set into a cylindrical mold and subjected to hydraulic pressure by which the various sections are intimately joined together and a smooth cylindrical surface obtained on the outside. While .under such pressure it is of course necessary that an iron core be inserted into the center hole of the wheel to prevent deformation. After pressing, this core is removed and the wheel taken out of the mold and set into a suitable vulcanizer, where it is brought up to a vulcanizing temperature of approximately 300 F. and held at that temperature for about three hours.

In making the modified form of grinding wheel, a mixture is prepared of a suitable resilient material, such as unvulcanized rubber, and small irregular lumps composed of bonded abrasive grains. For the resilient part of this mixture the composition (A) given above may be employed. The abrasive lumps may! be made by separately vu1caniz-; ilig a block molded from the composition and then crushing it to the desired size. The resilient material is then mixed with the vulcanized lumps containing abrasive grains, and the mixture is packed into the mold around the outer edge of the solid center to which it is made to adhere by tampin or pressing into place. The whole whee thus molded is then subjected to a vulcan ization of such a degree as may be necessary for the hardness and rigidity required.

On account of the smaller amount of sulphur contained in the matrix or central portion of the wheel, this part will be relatively soft and resilient or elastic. The abrasive portion, .which contains a larger amount of sulphur, eventhough it has been .in contact with the work, will be essentiall that of an abrasive article having the bar ness of the outer surface. a rigid contact with the work, however, on account of the soft or elastic backing, which will permit it to yield to the pressure of contact and thus prevent the deep cutting action which a wheel, having the hardness of the abrasive portions throughout, would give. At the same time the outer surface will possess sufficient rigidity to give the desired grinding action' 'and produce a highly polished surface.

While I have specifically described my invention as adapted to the manufacture of anabrasive wheel of a rubber composition, it will be obvious to those skilled in the art that other abrasive articles in which the same or similar properties are desired may be as readily made, and that other materials and other proportions may also be used to suit the particular conditions which may in It will not make i,to7,sse 7 any case be involved. Such modifications or substitutions of my invention are, however, to he considered as embodied in the above specification and in the following claims.

2. An abrasive article comprising a body, a plurality of spaced portions of rubber bonded abrasive grains, and resilient rubber Webs separating and supporting the bonded abrasive portions on said body.

3. An abrasive Wheel comprising a resilient cushioning body of rubber and a plurality of spaced teeth of bonded abrasive grains united and having a continuous surface with said body.

4. An abrasive wheel comprising a resilient rubber center portion, a plurality of spaced teeth of rubber bonded abrasive grains supported thereby, and Webs of resilient rubber separating and uniting the teeth with said center portion, said Webs and teeth having a common continuous surface.